The tongue develops from the floor of the pharynx beginning in the 4th week of gestation. The anterior two-thirds develops from swellings in the first pharyngeal arch, while the posterior one-third develops from the second, third, and part of the fourth arches. The thyroid gland develops as an epithelial proliferation in the floor of the pharynx between the fifth and seventh weeks and descends to its final location in front of the trachea by the seventh week. The development of the tongue, thyroid gland, and associated structures can result in congenital anomalies if development is disrupted.

1. DEVELOPMENT OF TONGUE
-Bharanidharan S

2. TONGUE:
•The Tongue is the Largest
muscular organ inside the
oral cavity.
•It is developed at the floor
of pharynx.
•Epithelium of tongue is
made up of single layer
which later gets stratified
and forms papillae.
•4 Papillae - Circumvallate,
Foliate, Fungiform and
Filiform

3. DEVELOPMENT OF TONGUE:
 DEVELOPMENT OF TONGUE BEGINS AT
ABOUT 4TH WEEK OF INTRAUTERINE LIFE.
 The dorsum of the tongue is divided into:
1. An oral part or anterior two thirds
2. A pharyngeal part(V shaped groove)or
posterior one third
3. Small posterior most part.
 The two limbs of the ‘V’ meet at a median pit,
named the Foramen Caecum.
 The foramen caecum represents the site from
which the thyroid diverticulum grows down in
the embryo.

5. ANTERIOR TWO-THIRD:
The anterior two-thirds of the tongue is formed by:
1. 2 Lateral mesodermal swellings
2. 1 median swelling ( tuberculum impar ) All
these 3 swellings are derived from the 1st
pharyngeal arch.
POSTERIOR ONE-THIRD:
Cranial part of hypobranchial eminence derived
from the mesoderm of 2nd, 3rd and part of 4th
pharyngeal arch.
POSTERIOR MOST PART:
Posterior most part and epiglottis are derived from the
4th pharyngeal arch.

6. NERVE SUPPLY OF TONGUE:
ANTERIOR 2/3rd – The mucosa
covering this part is supplied by
lingual branch of mandibular
division of trigeminenal nerve.
And special sensory inervation i.e
taste by the chorda tympani
branch of facial nerve (nerve of
1st arch)
POSTERIOR 1/3rd - supplied by
glossopharyngeal nerve (nerve of
3rd arch) for both general
sensations and taste.
POSTERIOR MOST PART -
supplied by the superior laryngeal
branch of vagus nerve (nerve of
4th arch).

7.  MUSCLES OF TONGUE:
Muscles of the tongue arise from the occipital
myotomes which lies in the occipital region and
migrates to help in the formation of muscular
component of the tongue. It is supplied by the
hypoglossal nerve (12th cranial nerve).
 Epithelium of the tongue is made up of a single
layer.Later it gets stratified and forms papillae.The
gustatory nerve cells of chorda
tympani,glossopharyngeal and vagus nerves
invade the epithelium to form taste buds.

9. CONGENITAL ANOMALIES:
MACROGLOSSIA - LARGE TONGUE.
MICROGLOSSIA - SMALL TONGUE.
INTRALINGUAL THYROID - THYROID TISSUE
MAY BE PRESENT IN TONGUE.
REMNANTS OF THYROGLOSSAL DUCT MAY
FORM CYSTS AT THE BASE OF THE TONGUE.

11. DEVELOPMENT OF
THYROID GLAND

12. •During the 5th week of embryonic
life the thyroid gland appears as
on epithelial proliferation in the
floor of the pharynx between the
tuberculum impar and cupola.
•The epithelial proliferation
descends in front of the
pharyngeal gut as a bilobed
diverticulum.
•During this migration,the gland
remains connected to the duct by
the Thyroglossal duct which
later disappears.

15.  With further development the thyroid gland
descends in front of the hyoid bone and laryngeal
cartilages.
 By 7th week of intrauterine life the thyroid gland
reaches its final position in front of the trachea.
 The ‘C’ cells are derived
from the ultimobranchial
body
 The ‘C’ cells serve as a
Source of calcitonin.

16.  The Thyroid gland begins to function at the 3rd
month of intrauterine life.
 The thyroid follicles first form at the periphery and
later into the central part.i.e.,the development of
follicles is centripetal.

17. ANOMALIES OF THYROID GLAND:
 Shape:
1. The pyramidal lobe as a normal
structure may be present and it
arises from isthmus.
2. Isthmus may also be absent.
3. one of the lobes may be missing
4. One of the lobes may be small.

18. •POSITION
 Lingual thyroid-Whole or part of the gland may be
under the mucosa of dorsum of tongue to form a
swelling,big enough to cause difficulty in
swallowing.
 The gland may be deep inside
Tongue,intralingual thyroid.
 Gland is present above the
Hyoid bone.
 Gland descends just below
Hyoid bone,but above its normal
Position.
 Intrathoracic,retrosternal.

19. ECTOPIC THYROID:
 Thyroid tissue has been observed in
larynx,trachea,esophagus,pleura,pericardium and
ovaries.
REMENANTS OF
THYROGLOSSAL DUCT:
 Thyroglossal cyst
 Thyroglossal fistula
 Carcinoma of thyroglossal duct.